The objectives of this core are to provide: 1. A service facility that wil utilize investigator-derived DNA constructs to create founder transgenic and gene knockout mice that can be used to address questions relevant to obesity and nutrition research; 2. Consultations to obesity and nutrition researchers regarding general aspects of transgenic and gene knockout work, the use of tissue-specific promoters, the generation of transgenic and gene knockout constructs, and the establishment and monitoring of genetically modified mouse colonies; and 3. Training in methods required for the generation of transgenic and gene knockout DNA constructs.